System and method for reduced stress vane shroud assembly

Abstract

This disclosure provides systems and methods for reducing stress in vane shroud assemblies by defining a gap between adjacent portions of the airfoil and the shroud whereby stress from the securing force is relieved in a portion of the shroud. The airfoil has a distal end with a contact surface and a tenon. The shroud has a contact surface with the airfoil and accommodates the tenon. An attachment device provides the securing force between the airfoil and shroud contact surfaces through the shroud and the gap serves to reduce stress on the shroud.

What is claimed is: 
     
         1 . A system comprising:
 an airfoil having a base end and a distal end, wherein the distal end comprises a shroud contact surface and a tenon;   a shroud with a first contact surface in contact with the shroud contact surface of the airfoil and a second contact surface for receiving a securing force, wherein at least a portion of the securing force is translated through the first contact surface to the airfoil; and,   an attachment device attaching to the airfoil and providing the securing force to the shroud; and,   wherein the distal end of the airfoil and the shroud define a gap between adjacent portions of the airfoil and the shroud allowing stress from the securing force to be relieved in a portion of the shroud.   
     
     
         2 . The system of  claim 1 , wherein the shroud contact surface of the airfoil is an end surface of the tenon. 
     
     
         3 . The system of  claim 2 , wherein the tenon further comprises at least one lateral surface and wherein the shroud includes at least one internal surface defining a recess for receiving at least a portion of the tenon, and at least a portion of the lateral surface of the tenon directly engages at least a portion of the internal surface of the shroud. 
     
     
         4 . The system of  claim 2 , wherein the attachment device is a bolt assembly with a shroud contact surface in contact with the shroud and providing the securing force to the shroud through the shroud contact surface of the bolt assembly and the shroud contact surface of the airfoil. 
     
     
         5 . The system of  claim 1 , wherein the tenon has at least one lateral surface defining a cross-sectional shape selected from a polygon, a rectangle, an ellipse, and a circle. 
     
     
         6 . The system of  claim 1 , wherein the attachment device is a plurality of bolt assemblies and the tenon defines a plurality of threaded recesses for receiving the plurality of bolt assemblies. 
     
     
         7 . The system of  claim 1 , further comprising a bushing, wherein the attachment device engages the bushing and the shroud, and the retaining force received by the bushing is substantially translated through the bushing to the shroud. 
     
     
         8 . The system of  claim 1 , wherein the distal end of the airfoil further comprises:
 a first planar surface surrounding and recessed from the tenon and including the shroud contact surface of the airfoil; and,   a second planar surface adjacent and substantially parallel to the first planar surface and recessed therefrom to define the gap between adjacent portions of the shroud and the distal end of the airfoil.   
     
     
         9 . The system of  claim 8 , wherein the distal end of the airfoil further comprises a third planar surface substantially parallel to and recessed from the first planar surface to define the gap between adjacent portions of the airfoil and the shroud proximate the third planar surface and wherein the third planar surface is closer to the shroud than the second planar surface. 
     
     
         10 . The system of  claim 1 , wherein the shroud further comprises:
 a first planar surface defining an opening for accommodating the tenon and including the first contact surface of the shroud; and,   a second planar surface adjacent and substantially parallel to the first planar surface and recessed therefrom to define the gap between adjacent portions of the shroud and the airfoil.   
     
     
         11 . The system of  claim 1 , further comprising a plurality of airfoils and a plurality of attachment devices attached to the shroud. 
     
     
         12 . A method comprising:
 positioning an airfoil having a base end and a distal end, wherein the distal end comprises a shroud contact surface and a tenon;   inserting the tenon of the airfoil into a shroud with a first contact surface placed in contact with the shroud contact surface of the airfoil and a second contact surface for receiving a securing force;   inserting an attachment device into the tenon of the airfoil through the shroud; and,   securing the attachment device such that at least a portion of a securing force from the attachment device is translated through the first contact surface of the shroud to the shroud contact surface of the airfoil such that the distal end of the airfoil and the shroud define a gap between adjacent portions of the airfoil and the shroud allowing stress from the securing force to be relieved in a portion of the shroud.   
     
     
         13 . The method of  claim 12 , wherein the shroud contact surface of the airfoil is an end surface of the tenon. 
     
     
         14 . The method of  claim 13 , wherein the tenon further comprises at least one lateral surface and wherein the shroud includes at least one internal surface defining a recess into which at least a portion of the tenon is inserted and at least a portion of the lateral surface of the tenon directly engages at least a portion of the internal surface of the shroud. 
     
     
         15 . The method of  claim 13 , wherein the attachment device is a bolt assembly with a shroud contact surface in contact with the shroud and securing comprises tightening the bolt assembly to provide the securing force to the shroud through the shroud contact surface of the bolt assembly and the shroud contact surface of the airfoil. 
     
     
         16 . The method of  claim 12 , wherein the tenon has at least one lateral surface defining a cross-sectional shape selected from a polygon, a rectangle, an ellipse, and a circle. 
     
     
         17 . The method of  claim 12 , wherein the attachment device is a plurality of bolt assemblies and the tenon defines a plurality of threaded recesses for inserting and securing the plurality of bolt assemblies. 
     
     
         18 . The method of  claim 12 , further comprising inserting a bushing into the shroud, wherein inserting the attachment device engages the bushing and the shroud and securing the attachment device exerts the securing force on the shroud substantially through the bushing. 
     
     
         19 . The method of  claim 12 , wherein the distal end of the airfoil further comprises:
 a first planar surface surrounding and recessed from the tenon and including the shroud contact surface of the airfoil; and,   a second planar surface adjacent and substantially parallel to the first planar surface and recessed therefrom to define the gap between adjacent portions of the shroud and the distal end of the airfoil.   
     
     
         20 . The method of  claim 19 , wherein the distal end of the airfoil further comprises a third planar surface substantially parallel to and recessed from the first planar surface to define the gap between adjacent portions of the airfoil and the shroud proximate the third planar surface and wherein the third planar surface is closer to the shroud than the second planar surface after securing the attachment device.